The formula of coarse, medium and fine SiC should be 5:1:4.
The manufacturing of silicon carbide brick raw materials generally choose black SiC, its chemical composition is as follows: SiC 98.0%, free C 0.5%, Fe 0.2%, free SiO2 0.6%.
Due to the different combination methods, the process is different.
The brief process of different combinations is:
(1) Silicon nitride bonded silicon carbide brick: a kind of %26α -sic skeleton and %26α and %26β-Si3N4 were produced in pure N2 gas at 1370℃ by using coarse, medium and fine silicon carbide particles and fine silicon powder.
Silicon nitride bonded silicon carbide brick for matrix.
There is still a small amount of residual silicon and SiO2N2 in the matrix and the relative contents of these components vary from manufacturing plant to plant.
(2) combined with silicon carbide brick: SiC, silicon powder, carbon powder according to a certain ratio, mixing, molding, burning in 1400℃ reducing atmosphere.
In most cases buried charcoal firing is used.
During the sintering process, a kind of %26β-Si3N4 bonded SiC brick with fine grain %26β -sic as matrix and %26α -sic as skeleton was produced.
%26β -sic is generated by the reaction of fine silicon powder and fine carbon powder during the firing process. This product also contains a small amount of residual silicon and carbon.
(3) silicon oxide nitriding combined with silicon carbide brick: when this brick ingredient, the ratio of fine silicon powder is less than silicon carbide.
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